Andrea Elena Castro, daughter of Rep. Joaquin Castro (D-Texas), holds a U.S. flag during a Rally For Our Children event on May 31 to protest the "zero-tolerance" immigration policy that has led to the separation of families. (Eric Gay/AP)

A federal judge in California is allowing a lawsuit to proceed against the Trump administration's practice of separating migrant families at the border.

"Such conduct, if true, is brutal, offensive, and fails to comport with traditional notions of fair play and decency," wrote U.S. District Judge Dana Sabraw of the Southern District of California in his ruling on Wednesday.

Hundreds of children have been separated from their parents as a result of the Trump administration's "zero tolerance" policy for people who cross the southern border illegally — even those who are claiming asylum in the U.S.

The administration moved to dismiss the case in early April. But Judge Sabraw refused, ruling that the "wrenching separation" of children from their parents may violate the families' right to due process.

"In the most forceful language, the court rejected the Trump administration's claim that the Constitution permits it to engage in the inhumane practice of tearing little children away from their parents," said Lee Gelernt, the deputy director of the ACLU's Immigrants' Rights Project.

The Justice Department declined to comment.

The plaintiffs in the case include Mrs. L, a Congolese immigrant who says she was separated from her 7-year-old daughter after applying for asylum at a port of entry. Another plaintiff, Mrs. C, fled from Brazil and crossed the border with her 14-year-old son. According to the lawsuit, she waited eight months to be reunited with her son after serving a jail sentence for illegal entry.

The ACLU is seeking a nationwide injunction. But that relief could be weeks or months away, if it comes at all.